Blood flow detector



FIG. 1 is the front end view showing the blood flow detector,

FIG. 2 is the rear end view thereof,

FIG. 3 is the side view thereof,

FIG. 4 is the top plan view thereof and;

FIG. 5 is a perspective front view thereof showing in dotted lines, for illustration only, the attachment of the device to a stethoscope. 

The ornamental design for a blood flow detector, as shown and described. 